God began to leave the world in 1543. That was the year when modern science is deemed to have begun; when the appearance of Copernicus’s De Revolutionibus and Vesalius’s Anatomy marked the end of scholastic reliance on authority, and the beginning of the scientific method based on observation, hypothesis and experiment. I do not mean that God literally gathered together his possessions and moved back to Heaven: rather, that the mid-16th century marked the death of pre-scientific man, who had reasonably assumed that since God was in everything, he made everything work. It therefore made sense to believe that if the effective cause of any event from mental disease to crop growth is known, there can be no room for God as effective agent. God can exist only in the ever-decreasing gaps in our knowledge. And by simple extrapolation, there must come a time when there will be no space for him – except above the bright blue sky.

Now all this makes sense, until we come down to ourselves. After all, cogito ergo sum. It is all very well to talk about the evolution of consciousness, of neural potentials and feedback mechanisms, but most of us have more than a sneaking suspicion that there is more to being human than merely being an affluent ape. Which is why the unravelling of the causal chain from copulation to childhood via cell biology, DNA chemistry, gene action, epigenetic switching, and so on, is vaguely disturbing. And why it is more difficult to adjust to the possibility of reproduction in a test-tube than it was to adjust to the clinical and pharmaceutical niceties of a well-planned family. In other words, we are scared by the prospect of genetic determinism and all its implications.

Just over half a century ago, Aldous Huxley introduced us to a Brave New World:

On a very slowly moving band a rack-full of test-tubes was entering a large metal box, and another rack-full was emerging. Machinery firmly purred. It took eight minutes for the tubes to go through, he told them. Eight minutes of hard X-rays being about as much as an egg can stand. A few died, of the rest the least susceptible divided into two; most put out four buds; some eight; all were returned to the incubators, where the buds began to develop; then, after two days, were suddenly chilled, chilled and checked. Two, four, eight, the buds in their turn budded; and having budded were dosed almost to death with alcohol; consequently burgeoned again and having budded – bud out of bud out of bud were thereafter – further arrest being generally fatal – left to develop in peace. By which time the original egg was in a fair way to becoming anything from eight to 96 embryos – a prodigious improvement, you will agree, on nature. Identical twins – but not in piddling twos and threes as in the old viviparous days, when an egg could sometimes accidentally divide; actually by dozens, by scores at a time.

‘Scores,’ the Director repeated and flung out his arms, as though he were distributing largesse. ‘Scores.’

But one of the students was fool enough to ask where the advantage lay.

‘My good boy!’ The Director wheeled sharply round on him. ‘Can’t you see? Can’t you see?’ He raised a hand; his expression was solemn. ‘Bokansky’s Process is one of the major instruments of social stability!’

The voice was almost tremulous with enthusiasm. ‘You really know where you are. For the first time in history.’ He quoted the planetary motto. ‘Community, Identity, Stability.’ Grand words.